Process and apparatus for mechanically joining metallic components

ABSTRACT

A process for mechanically joining plies of thin metallic components lying on one another, and apparatus for its implementation, involves an impulse-wave conductor ( 9, 25, 31 - 35 ) having first and second substantially straight impulse-wave-conductor portions ( 19, 20, 32, 33 ) which are arranged at an angle to one another along which impulse waves are transmitted to a stamp ( 7 ) to be driven into a component to be joined by impulse force. The impulse waves are redirected between the first and second substantially straight impulse-wave-conductor portions by a structure of an intermediate angled portion ( 21, 31 ) located between, the first and second substantially straight impulse-wave-conductor portions.

BACKGROUND OF THE INVENTION

[0001] This application claims a foreign priority based on German application 100 10 340.5, filed Mar. 6, 2000, and the contents of that application are incorporated by reference herein.

[0002] This invention concerns a process for mechanically joining (for example, clinching and stamping together) two plies of thin metallic components, such as sheet metal, lying on one another, and an apparatus to carry this out, involving a stamp of a joining tool being driven into a component to be joined by impulse force with the impulse force being transmitted to the stamp as impulse waves via an impulse-wave conductor. Examples of such processes and apparatus are disclosed in German patent document DE 197 77 267 C2 and European patent document EP 0 890 397 A1.

[0003] In both of these publications a striking tool having an impulse-creating plunger, an impulse-wave conductor and a stamp are arranged in a row along a vertical axis. Thus, a rather tall structure results, so that joining processes to be carried out by this apparatus cannot be done in operation areas that have limited space, although they are particularly well suited therefor.

[0004] It is an object of this invention to provide a joining process involving a stamp of a joining tool being driven into a component to be joined by impulse force with the impulse force being transmitted to the stamp as impulse waves via an impulse-wave conductor, and a joining tool for carrying out this process, that makes possible a significantly shorter profile for that part for the tool containing the stamp, the impulse-wave conductor and the striking tool.

SUMMARY OF THE INVENTION

[0005] According to principles of this invention, a joining process involves providing an impulse-wave conductor with first and second substantially straight impulse-wave-conductor portions (straight legs) which are arranged at an angle to one another and transmitting impulse waves between the first and second substantially straight impulse-wave-conductor portions by redirecting them with an intermediate angled portion formed as one piece with, and between, the first and second substantially straight impulse-wave-conductor portions or with a reciprocating rebound body for receiving a force from impulse waves in the first substantially straight impulse-wave-conductor portion and redirecting them by impacting the second substantially straight impulse-wave-conductor portion.

[0006] An apparatus for carrying out this process has one of: a bowed intermediate portion made as one piece with, and being positioned between, the two substantially-straight legs, with the intermediate portion extending in a largest possible arc; an angled intermediate portion having a beveled flat-area surface, with the flat-area surface being of such a size, and extending at such an angle, that projections thereof, toward each free end of the straight legs of the impulse-wave conductor, correspond in size to perpendicular cross-sectional cuts of the straight legs; or the first and second impulse-wave conductor portions are separated parts and arranged at an angle to one another, with an angled rebound body being positioned between the first and second impulse-wave conductor parts to pivot about a pivot point lying between the impulse-wave conductor parts, with a first leg end of the rebound body lying against an impulse-input-side of the first impulse-wave conductor part under a spring bias and with a second other leg end of the rebound body being spaced from the second impulse-wave conductor part which has the stamp coupled thereto.

[0007] By redirecting impulse waves, it is possible to arrange a striking tool to the side of, and substantially spaced from, a stamp, thereby resulting in a significantly narrower structure of the joining tool. Such a joining apparatus has fewer impractical “disturbing contours” and is comparable with a resistance spot welder tong in its operational possibilities, relative to its access to joining locations.

[0008] When structuring the impulse-wave conductor, one should strive that compression waves created by the striking tool in the impulse-wave conductor also arrive as such, as much as possible, in the stamp, and not become expansion, or pulling, waves on the way due to reflection. This is achieved by any of the three structures described above.

[0009] The first structural version employs the bent, or angled, impulse-wave conductor, with at least the first and second legs thereof being as straight as possible and the intermediate portion extending in a largest possible bow or arc. With this structure, most of the compression waves are reflected in large obtuse angles when transitioning from one leg to the other so that the compression waves arrive at the stamp.

[0010] In the second version, the reflection surface is arranged to be targeted in the transition area from one leg to the other leg of the impulse-wave conductor. In this version the impulse-wave conductor is angled, with an outer angle edge being diagonally flattened, the flattened area being of such a size and extending at such an angle that a projection thereof toward each leg approximately corresponds in size and shape to cross-sectional cuts of the attached legs. This reflection surface reflects the compression waves hitting it at only a small angle to a central axis of the second leg, so that most of the waves also reach the stamp as compression waves.

[0011] To increase the effectiveness of this version of the apparatus, it has proven to be beneficial to press a body mass on the reflection surface with a spring system, with a surface of the body mass lying on the reflection surface being larger than the reflection surface and extending beyond it in all directions and with a natural frequency of the spring-mass-system being half as great as the impulse wave frequency. This additional mass serves to ensure that a compression wave hitting the redirecting surface is mainly reflected as a compression wave and not as an expansion wave. In this regard, it is beneficial for the additional mass to be of a material that has a greater wave, or sound, resistance than does the impulse-wave conductor.

[0012] In the third version of the apparatus, the impulse-wave redirection is caused by inter-disposition of a force redirection part. In such an apparatus the impulse-wave conductor is of two separate parts, with the two impulse-wave conductor parts arranged at an angle to one another, there being the bent, or angled, rebound body arranged between the two impulse-wave conductor parts to be pivotal about an interior pivot point positioned between legs thereof, a leg end of a first leg of the rebound body lying on the, input-side, first impulse-wave conductor part under spring force, and a leg end of a second leg of the rebound body being spaced from the second impulse-wave conductor part. In this regard, it is important that the force of the spring is chosen such that the rebound body is once again made to lie against the first impulse-wave conductor part for receiving the next wave after it swings out.

[0013] An air pressure driven plunger can be used as a striker of the striking tool. It is, however, particularly for reducing striking noise, beneficial for the impulses to be created by one or more lined-up piezoelectric actuators. This series arrangement of the actuators has the advantage of amplifying the magnitude of the striking, or impulse, amplitude so that a greater stamp path can be used. The piezoelectric actuators are particularly well suited for producing a pulsating striking force.

[0014] In a further beneficial embodiment of the apparatus, impulse waves fed into a die plate, or female mold, are conducted via an impulse-wave conductor, which is formed in the same manner as is the impulse-wave conductor feeding impulse waves to the stamp. Thus, a lower part of the joining apparatus has a lower profile than for known apparatus.

[0015] In a beneficial further embodiment of the apparatus of this invention, the impulse-wave conductors coupled to the stamp and die plate are structured as upper and lower tong arms of a shearing-principle support device of the joining apparatus. This embodiment makes possible a quite uncomplicated and low profile construction of the entire apparatus.

[0016] Further, it is beneficial for a rebound mass to lie against the impulse-wave conductor at the end of the lower tong arm under pressure of a spring system to eliminate, or absorb, the impulse waves. This rebound mass can be replaced by piezoelectric actuators 30, if piezoelectric-actuator-joining force is used, acting on the die plate at the same time as, or synchronized with, the actuators acting on the stamp.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Further benefits, characteristics and details of the invention are explained in more detail below using embodiments shown in the drawings. The described and drawn features can be used individually or in preferred combinations in other embodiments of the invention. The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of the preferred embodiment of the invention, as illustrated in the accompanying drawings in which reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating principles of the invention in a clear manner.

[0018]FIG. 1 is a side view of a joining apparatus of this invention;

[0019]FIG. 2 is an enlarged view of a detail A in FIG. 1;

[0020]FIG. 3 is an enlarged view of a detail corresponding to detail A in FIG. 1, but for a second embodiment;

[0021]FIG. 4 is an enlarged view of a detail corresponding to detail A in FIG. 2, but with an embellishment of the second embodiment;

[0022]FIG. 5 is an enlarged view of a detail corresponding to detail A in FIG. 1 but for a third embodiment involving a rebound body between two impulse-wave conductors;

[0023]FIG. 6 is another embodiment of a rebound body, relative to FIG. 5;

[0024]FIG. 7 is a side view of a further embodiment of a joining apparatus of this invention; and

[0025]FIG. 8 is a side view of yet another embodiment of a joining apparatus of this invention, different from that of FIG. 7;

DETAIL DESCRIPTION OF THE INVENTION

[0026] Each embodiment of a joining apparatus shown in FIGS. 1, 7 and 8 is structured in the manner of shears, with an upper tong arm 1 and a lower tong arm 2 being pivotally coupled to one another at a rotation point 3. End portions 4 and 5 of the upper as well as the lower tong arms 1 and 2 extend beyond the rotation point 3. A motivating unit 6 is arranged between these two end portions 4 and 5 for opening forward tong ends and moving them back together. Such a shearing-tong, with the above described arrangement of the motivating unit, with the motivating unit being arrange behind a center of gravity of the shearing tongs, makes possible a narrow structure for the joining apparatus and improves its maneuverability by having a favorable distribution of its masses.

[0027] In the embodiment of FIG. 1, each of the upper tong arm 1 and the lower tong arm 2 forms a ram, or impulse, wave conductor 9, 10. These impulse-wave conductors 9 and 10 pass rearward through holders 11, 12 that support them. A striking, or pulsating, tool 14 operates on the end 13 of the impulse-wave conductor 9 that extends through the holder. Impulses created by the striking tool 14 are transmitted by the impulse-wave conductor as compression waves into an angled arm 20 of the impulse-wave conductor 9 and from there to a stamp 7. The striking tool 14 is pressed against an end 13 of the impulse-wave conductor 9 by a spring 15.

[0028] The lower tong arm 2, which has a female mold, or die plate 8, is also formed as an impulse-wave conductor 10. A rear end 16 of this impulse-wave conductor 10 extends through the holder 12. A rebound mass 17 is pressed against this rear end 16 of the impulse-wave conductor 10 by a spring 18. This spring/impact-mass system dampens impact waves that are further transmitted by the stamp 7 to the impulse-wave conductor 10.

[0029] In order to achieve an optimal redirection of the impact waves from the horizontal leg 19 of the impulse-wave conductor 9 to the vertical leg 20, an intermediate portion 21 of the impulse-wave conductor 9 is structured such that the compression waves guided into this intermediate portion 21 arrive at the end of the vertical leg 20, and thereby at the stamp 7, as compression waves and not as expansion waves. In order to best achieve this prerequisite, the intermediate portion 21, as can be seen in FIG. 2, is in the form of a bow, or arc, and an arc having the greatest possible radius should be chosen. Another possible structure is represented in FIG. 3 in which an impact wave traveling along the horizontal leg 19 is reflected from a flat surface 22 into the vertical leg 20.

[0030] In order that the compression waves from the horizontal leg 19 hitting the surface 22 are also reflected therefrom predominantly as compression waves and not as expansion waves, an additional mass body 23 lies against the surface 22 and is pressed thereagainst by a spring system 40. A surface 24 of the mass body 23, which lies against the surface 22 of the impulse-wave conductor 9, extends on all sides beyond the surface 22 of the impulse-wave conductor 9, and a natural frequency of the spring-mass-system of the additional mass body 23 is half as great and the impulse wave frequency. An effectiveness of the additional mass body 23 is high, if it is of a material that has a greater wave resistance than does that of the impulse-wave conductor 9.

[0031] In the embodiment of FIG. 7, impulse-wave conductors 25, 26 are not formed of upper and lower tong arms as in the embodiment of FIG. 2, rather, here two tong arms 1, 2 are hollow, and the two impulse-wave conductors 25 and 26 as well as the striking tool 14 and the rebound mass 17 are positioned in the hollow tong arms 1 and 2. This is also true for two spring pressing apparatus 27 and 28 of the striking tool 14 and the rebound mass 17. In this regard, it is beneficial for the pressing apparatus 27 of the striking tool 14 to be adjustable.

[0032] In the joining apparatus of FIG. 8, piezoelectric actuators 29 are used as a striking tool instead of a pneumatic striking tool. A plurality of piezoelectric actuators arranged in series increases impact amplitude to such an extent that the elastic limit of a material to be joined is exceeded by each impulse. In this apparatus, instead of using the rebound mass 17 of the embodiment of FIG. 7, piezoelectric actuators are place in the lower tong arm which operate on the female mold 8 in time with the actuators 29 on the stamp 7, and thereby increase a joining strength.

[0033] In the embodiment of FIG. 5, impact waves created by the striking tool 14 are redirected by a pivotally-mounted rebound body 31. Compression waves created by the striking tool 14 in the impulse-wave conductor 32 are transmitted into a leg 35 of the rebound body 31. When this is done, the rebound body pivots about its pivot point 34 in a direction of an arrow B and a free end of its leg 36 strikes against a impulse-wave conductor 33 and creates therein a compression wave which is transmitted further to the stamp 7. After it has swung out, the rebound body 31 is pivoted back to its original position opposite the direction of the arrow B by a return spring 37. So that the rebound body 31 does not apply a significant impact on the impulse-wave conductor 32 upon its return pivot, it strikes against an elastic impact damper 38 upon its return pivot. A force of the return spring 37 is chosen such that the rebound body 31, after its outward pivot, once again lies against the first impulse-wave conductor 32 for receiving the following impulse wave.

[0034] In an embellishment of the rebound body 31, it has, as shown in FIG. 6, a body sound-stopping, or damping, intermediate layer 39. This intermediate layer 39 eliminates or reduces bending oscillations, or vibrations, in the rebound body 31.

[0035] The impulse-wave conductor 9, 10, 25, 26, 32, 33 tong shaped joining tool is of a material (solid, liquid or gas) which provides very little damping, particularly of a metal having very little of its own damping. 

I claim:
 1. Process for mechanically joining plies of thin metallic components lying on one another, including providing a joining tool, wherein a stamp of the joining tool is driven into a component to be joined by impulse force with the impulse force being transmitted to the stamp as impulse waves via an impulse-wave conductor (9, 25) of the joining tool; wherein, the impulse-wave conductor is provided to have first and second substantially straight impulse-wave-conductor portions (19, 20) which are arranged at an angle to one another along which the impulse waves are transmitted to the stamp, wherein the impulse waves are transmitted between the first and second substantially straight impulse-wave-conductor portions (19, 20) by redirecting them with an intermediate angled portion (21) formed as one piece with, and between, the first and second substantially straight impulse-wave-conductor portions (19, 20).
 2. A tong shaped joining tool for mechanically joining two thin metallic components lying on one another, said joining tool including: a stamp for being driven into at least one of the components by impulse force acting on the stamp; an impulse-wave conductor (9) attached to the stamp for conducting impulse force to the stamp as a compression wave, wherein the impulse-wave conductor (9) includes as one piece a bent intermediate portion (21) between two substantially-straight legs (19, 20), with the intermediate portion (21) extending in a largest possible arc for conducting said compression wave between said two substantially-straight legs (19, 20), via the intermediate portion (21).
 3. A tong shaped joining tool for mechanically joining two thin metallic components lying on one another, said joining tool including: a stamp for being driven into at least one of the components by impulse force acting on the stamp; an impulse-wave conductor (25) attached to the stamp for conducting impulse force to the stamp as a compression wave, wherein the impulse-wave conductor (25) includes as one piece two straight legs (19, 20) and an angled portion, with an outer angled edge of the angled portion forming a beveled flat-area surface (22), with the flat area surface being of a such size and extending at such an angle that projections thereof, toward each free end of the straight legs (19, 20) of the impulse-wave conductor, correspond to perpendicular cross-sectional cuts of the straight legs.
 4. A joining tool as in claim 3 wherein is further included a mass body (23) pressed against the flat-area surface (22) by a spring system (40), wherein a surface (24) of the mass body (23) lying against the flat-area surface (22) is larger than the flat-area surface (22) of the impulse-wave conductor (25) and extends beyond the flat-area surface (22) on all sides, and wherein a natural frequency of a spring-mass-system is half so great as an impulse wave frequency.
 5. A tong shaped joining tool for mechanically joining two thin metallic components lying on one another, said joining tool including: a stamp (7) for being driven into at least one of the components by impulse force acting on the stamp; an impulse-wave conductor attached to the stamp for conducting impulse force to the stamp as a compression wave, wherein the impulse-wave conductor comprises first and second separate impulse-wave conductor parts (32, 33) arranged at an angle to one another, with a separate angled rebound body (31) positioned between the first and second impulse-wave conductor parts (32, 33) and being pivotal about a pivot point (34) lying between the impulse-wave conductor parts (32, 33), with a first end (35) of the rebound body (31) lying against an impulse-input-side of the first impulse-wave conductor part (32) under a spring bias and with a second other leg end (36) of the rebound body (31) being spaced from the second impulse-wave conductor part (33) which has the stamp (7) coupled thereto.
 6. The tong shaped joining tool of claim 5 wherein, a bias force of a spring (37) creating the spring bias is chosen such that the rebound body (31) is thereby caused to once again lie against the first impulse-wave conductor part (32) after it swings out in time for arrival of a next following impulse wave.
 7. The tong shaped joining tool of claim 6 wherein, the rebound body (31), upon its return swing, is made to lie quickly against the first impulse-wave conductor part (32) by contact with an elastic impact damper (38).
 8. The process of claim 1 wherein, the impulse-wave conductor provided is of a material which provides very little damping.
 9. The process of claim 1 wherein, the substantially straight impulse-wave-conductor portion (20) of the impulse-wave conductor (9, 25) operating on the stamp (7) extends in a direction of a length axis of the stamp (7).
 10. The process of claim 1 wherein, is further included at least one piezoelectric actuator (29, 30) for creating the impulse wave.
 11. The process of claim 1 wherein, is further provided a die plate (8) toward which the stamp is driven, and wherein impulse waves are conducted to the die plate by an impulse-wave conductor (10, 26) which is substantially similar in form to the impulse-wave conductor (9, 25) conducting impulse waves to the stamp (7).
 12. The process of claim 11 wherein, the impulse-wave conductors (9, 25) are formed by upper and lower tong arms.
 13. The process of claim 11 wherein, the joining tool is tong shaped and wherein upper and lower tong arms of the tong shaped joining tool are hollow and wherein the impulse-wave conductors (25, 26) are positioned therein.
 14. The process of claim 13 wherein, a material for mounting the impulse-wave conductor has a distinctively different sound resistance than does the impulse-wave conductors.
 15. The process of claim 1 wherein, the joining tool provided is in the form of a tong structure that is structured in a general manner of shears.
 16. The process of claim 15 wherein, a rebound mass (17) is pressed against the impulse-wave conductor (10, 26) at an outer end of the lower tong arm (2) by a spring system (18, 28) for eliminating impulse waves.
 17. The process of claim 12 wherein, the impulse-wave conductors (9, 10, 25, 26) are covered by a sound damping material.
 18. The process of claim 1 wherein, an impulse-wave-creating striking tool (14) is provided that is pressed against the impulse-wave conductor (9, 25) for creating the impulse waves.
 19. The process of claim 1 wherein, the joining tool has a portion thereof touching a component to be joined outside of a joining area that is coated with a vibration-dampening coating.
 20. The process of claim 10 wherein, the lower tong arm which supports the die plate (8) also has at least one piezoelectric actuator (30) associated therewith which operates on the female mold (8) in time with the actuator (29) operating on the stamp (7).
 21. The tong shaped joining tool of claim 5 wherein, the rebound body (31) has two legs (35, 36) and has a body-sound-dampening intermediate layer (39) between its two legs (35, 36).
 22. Process for mechanically joining plies of thin metallic components lying on one another, wherein a stamp of a joining tool is driven into a component to be joined by impulses force with the impulse force being transmitted to the stamp as impulse waves via an impulse-wave conductor; wherein, the impulse-wave conductor provided has first and second separate, substantially straight, impulse-wave-conductor parts (32, 33) which are arranged at an angle to one another along which the impulse waves are transmitted to the stamp, wherein impulse waves are transmitted between the first and second substantially straight impulse-wave-conductor parts by redirecting them with a reciprocating rebound body (31) for receiving a force from impulse waves in the first substantially straight impulse-wave-conductor part (32) and redirecting the force by impacting the second substantially straight impulse-wave-conductor part (33). 